The invention relates to an optical scanning device for scanning an information track of an optically scannable information carrier, which scanning device includes a radiation source, an optical lens system with an optical axis for focusing a radiation beam supplied, in operation, by the radiation source into a scanning spot on the information carrier, and a first actuator for moving the lens system parallel to the optical axis, the lens system including two lens elements and a second actuator for displacing a first one of the lens elements relative to a second one of the lens elements.
The invention further relates to an optical lens system which can suitably be used in an optical scanning device in accordance with the invention.
The invention also relates to an optical player including a table which can be rotated about an axis of rotation, an optical scanning device for scanning an information track of an optically scannable information carrier which can be arranged on the table, and a displacement device for moving the scanning device during operation, mainly in a radial direction relative to the axis of rotation.
An optical scanning device and an optical player of the types mentioned in the opening paragraphs are known from U.S. Pat. No. 5,712,842. The optical lens system of the known optical scanning device includes an objective lens and a relatively small, so-called solid immersion lens, which is arranged between the objective lens and the information carrier to be scanned. By using the solid immersion lens, the lens system of the known optical scanning device has a relatively large numerical aperture, so that a relatively small scanning spot on the information carrier to be scanned is achieved. As a result, the known scanning device can suitably be used to scan information carriers having relatively small elementary information characteristics, that is, information carriers with a relatively high information density, such as a high-density CD. Using the first actuator of the known scanning device, the lens system is displaced parallel to the optical axis, thus enabling the scanning spot to be focused on the information layer of the information carrier. Using the second actuator of the known scanning device, the solid immersion lens is displaced relative to the objective lens, parallel to the optical axis, so that a spherical aberration of the radiation beam in a transparent protective layer of the information carrier present between the information layer and the scanning device can be corrected.
The second actuator of the known scanning device includes a ring-shaped electric coil, which is secured to a first holder to which the solid immersion lens is secured, and a ring-shaped permanent magnet which is secured to a second holder to which the objective lens is secured. The first holder is secured to the second holder using a leaf spring. By interaction between a magnetic field of the magnet and an electric current in the coil, the solid immersion lens can be displaced relative to the objective lens, in a direction parallel to the optical axis of the lens system, thereby deforming the leaf spring.